INNOVATIVE MONITORING OF WATER COURSES FOR THE PREVENTION OF FLOODS
CASE STUDY: Misa river (Senigallia, AN, Italy)
Flooding is a natural phenomenon, widespread and common throughout the world, which can have a far-reaching effect on people and the environment. It is a rapid and excessive accumulation of water in a normally dry region caused by important and persistent atmospheric precipitations. The phenomenon is accentuated by some local characteristics such as the conditions and composition of the soil, its slope and the topography of the place.
ProgettoRIO, designed by Flavio Falcinelli and funded by the companies RadioAstroLab and Fasar Elettronica, monitors watercourses (ditches, canals, streams and rivers) indicating potential environmental risks due to overflows that cause floods. An interesting case study concerns the annual experimentation launched on the Misa river, a typical torrential watercourse that flows into the Adriatic Sea crossing the city of Senigallia (AN), in central Italy. The river, characterized by a very variable regime with frequent flood events, caused floods, some of which were particularly disastrous such the one occurred in May 2014. By measuring some parameters of the river area and local tropospheric perturbations on a daily basis, the data are processed to generate graphs that represent how the percentage of flooding of the basin, the dynamics of the waters, the frequency and intensity of precipitation varies over time. This information visualizes the conditions of the river in real time, signaling potential dangerous situations for the population and the environment. The aim is to demonstrate to the institutions the effectiveness of a river surveillance system that uses innovative and low-cost instruments, designed and built by local companies, to provide a public utility and civil protection service.
LET’S KEEP AN EYE ON THE RIVER MISA
The monitoring, which began in October 2020, provides for sample measurements carried out by the bridge on the provincial road of Bettolelle, a town about 7 km as the crow flies from the center of the city of Senigallia. The site chosen for the surveys is suitable for an immediate and safe positioning of the instrumentation, offering ample visibility of the river basin in a location quite distant from the city of Senigallia in order to report, with sufficient advance, possible flood events.
The instrumentation used is portable, battery powered, each time positioned for measurement and subsequently removed.
The final objective of the experimentation is the installation of an automatic fixed station that continuously records the evolution of river parameters to provide a very precise, high-time resolution representation of the observed scenario.
The intensity of rainfalls affecting the area, as the main cause of waters rising, is estimated by analyzing the data collected from a single measurement station located in the southern outskirts of Senigallia (in an urban area). This is not a conventional rain gauge station, but a microwave radiometer which, based on the technology used for river monitoring, observes the sky to record tropospheric perturbations and estimate the intensity of precipitation (details can be found here: The microwave troposphere).
Once the acquired data has been processed, a graphic representation is obtained that displays the quantity of water present in the basin (percentage of flooding), its variations, its dynamics, the frequency and intensity of meteorological precipitation.
Thanks to this information, updated every 24 hours, potential risk situations can be identified and dealt with promptly.
False color map describing how the flood rate of the river basin in the measurement section varies over time. The quantity of water / humidity present in the soil varies with the color: it changes from the blue color indicative of a dry region, to the red color which indicates the presence of free water on the surface. The horizontal axis indicates the width of the measurement section (bridge on the Brugnetto-Bettolelle provincial road), the vertical axis the days that have passed since the beginning of the year. The map is updated approximately every week.
HOW TO READ THE GRAPHS
The graphs summarize the results of the monitoring and display the daily variations in the quantity of water and moisture content in the three regions of the river basin monitored by the instrument: the first trace (blue) is associated with the course of the river, the second (of red) represents the region close to the interface between the ground and the watercourse (river bank), the third (green) a surface of the basin normally dry and sufficiently distant from the river. The physical meaning of these data is connected to the concept of surface reflectivity of the observed environments: the instruments (microwave radiometers) see, in fact, a wet surface exposed to the atmosphere as if it were a mirror, the more reflective the greater the area humid and the amount of water present. On the other hand, a dry ground appears as a stationary surface with poor reflectivity. Increasing trends in the curves indicate increases in the quantity of moisture and water in the soil: when the red and green traces tend to converge towards the blue trace, it means that the river basin is gradually flooding. If this trend continues until it reaches the upper limit of the graph, corresponding to a total flooding of the region (100%), it means that the risk of flooding is high.
Conversely, there is a drought event in the river basin when the curves tend to coincide towards the lower limit of the graph (0% flooding).
These measurements are obviously well correlated with the trend of the hydrometric level read on the river shaft installed on the bridge pylon (black curve).
The long-term variations of the graphs are related to the seasonal variations in humidity of the scenario monitored by the instruments.
The purple color curve shows the dynamic variations of water flow in terms of speed and turbulence, well correlated, together with the previous measurements, with the main triggering cause of alluvial phenomena: atmospheric precipitation, represented in frequency and intensity by the histograms in the last graph.
The color of the box that displays the date of the last measurement, shown at the bottom right of the graphic area, indicates the current conditions of the river basin:
YELLOW : drought event
GREEN : normal condition of the river
ORANGE : swollen river, with high flow of water
RED : risk of flooding.
We use original equipment, dedicated to the purpose, developed and produced by RadioAstroLab (with the support of FASAR Elettronica), to monitor the environment in all weather conditions, day and night. Special (patented) microwave radiometers receive the natural electromagnetic radiation of bodies (such as the ground, water and the atmosphere) emitted by the effect of the temperature and the energetic interactions between the atoms and the molecules that constitute them and analyze in real time the data to obtain important information on the observed scenario.
The functioning of the system can be understood by remembering that a ground is all the more reflective, if observed in the microwave band of the electromagnetic spectrum, the greater the quantity and extension of free water present in a thin surface layer. The reflectivity of the soil, very low when it is dry and bare, tends to increase in the presence of vegetation, moisture and, above all, free water. A microwave radiometer estimates this parameter indirectly, measuring the brightness temeprature of the scenario, a magnitude mainly dependent on the presence of water, secondarily on other variables such as temperature, soil composition, its surface roughness, the presence of vegetation and the radiation of the atmosphere reflected from the surface towards the instrument. Appropriate calibration procedures minimize the effects of secondary parameters on the measurement.
Furthermore, when you observe a moving surface such as a flow of water, with waves and ripples, the reflectivity of the scenario varies continuously: the microwave radiation coming from the atmosphere and the environment, reflected from the surface towards the instrument, diffuses in all directions with varying intensity (scattering) causing important fluctuations in the measurement, which depend on the speed and turbulence of the water. These properties are used to monitor the dynamics of a surface of water flowing in a river basin.
Our instruments estimate the surface content of water and moisture present in a river area by recording their variations over time, evaluating the dynamics of the water and observing the atmosphere to follow the evolution of meteorological conditions that can influence the regime of the river. The regularly updated graphic representation of these parameters highlights very well the seasonal evolution of the river environment with its drought and flood events, providing a powerful tool for dealing with potential flood risks.
This work is a first application of ProgettoRIO, innovative monitoring system of a river basin which, using remote sensing microwave techniques, measures and displays the daily evolution of the percentage of flooding in the environment, tracks the dynamics of the water flow to formulate forecasts and launch alarms when flood events occur.
The evolution of the project involves the installation of a fixed network of sensors strategically positioned in the territory and the development of an IT system suitable for managing the information coming from the various devices, obtaining the right tool to keep an eye on the river.
The development and expansion possibilities of ProgettoRIO are remarkable and numerous, both in the number and type of sensors, and for the possibility of acquiring, from specialized bodies through the web, data of national meteorological interest, regional and local on atmospheric and sea conditions near the mouth of the river (waves, currents, winds). By integrating this information with the data acquired by the sensors, it is possible to develop reliable forecast algorithms, valid with sufficient advance to allow an effective and timely organization of civil protection in the event of an emergency.